Explosive compositions and method of preparation

ABSTRACT

An explosive composition in slurry or semi-solid form and containing calcium nitrate is made up by reacting calcium oxide with formaldehyde, preferably in the form of paraformaldehyde, in the presence of ammonium nitrate. The water generated in the reaction serves as a vehicle for the slurry. A thickener of gum or preferably starch is added, and gassing agents may be incorporated to control or reduce composition density. The presence of ammonium nitrate prevents run-away reactions and the hexamethylene-tetramine which is produced in the reaction serves as a fuel tending to give oxygen balance to the composition.

United States Patent Cook et al. May 2, 1972 [54] EXPLOSIVE COMPOSITIONS AND 3,378,415 4/1968 Griffith 149/62 x METHOD OF PREPARATION 3,419,444 12/1968 Minnick ..149/62 X 3,507,718 4/1970 Mortensen et a1. ..149/61 X [72] Inventors: Melvin A. Cook; Frederick K. Balli, both of Salt Lake Clty, Utah Primary Examiner-Carl D. Quarforth [73] Assignee: Intermountain Research and Engineering Assmam Hellman Co" hm Atr0rneyEdwm M. Thomas 221 Filed: Aug. 15, 1969 57 ABSTRACT [21] April-No.1 850,648 An explosive composition in slurry or semi-solid form and containing calcium nitrate is made up by reacting calcium [52] U S Cl 149/46 149/18 149/47 oxide with formaldehyde, preferably in the form of parafor- 149/61 149/62 maldehyde, in the presence of ammonium nitrate. The water [5 I] Int Cl C06b 1/04 C06b 7/00 C06b 21/00 generated in the reaction serves as a vehicle for the slurry. A [58] Fie'ld 149/18 62 46 47 thickener of gum or preferably starch is added, and gassing agents may be incorporated to control or reduce composition density. The presence of ammonium nitrate prevents run- [56] References cued away reactions and the hexamethylene-tetramine which is UNITED STATES PATENTS produced in the reaction serves as a fuel tending to give oxygen balance to the composition. 3,247,033 4/1966 Gordon ..l49/18 Gordon 149/60 12 Claims, No Drawings EXPLOSIVE COMPOSITIONS AND METHOD OF PREPARATION BACKGROUND AND PRIOR ART The use of slurry type blasting compositions has become significant in hard rock mining and excavation operations and is currently increasing. These slurries, as shown in U.S. Pat. No. 2,930,685, US. Reissue Pat. No. 25,695, and others, are made up by dissolving an inorganic oxidizer salt, usually ammonium nitrate, or ammonium nitrate combined with sodium nitrate and/or other powerful oxidizers in water and adding fuel ingredients thereto to form a pourable and pumpable liquid, gel, or slurry of appropriate consistency. The fuel ingredients usually include dry particles of high energy oxidizable materials, such as aluminum, or self-explosive materials such as TNT, smokeless powder, etc. Combinations of explosive and non-explosive fuels may be used, and liquid fuels may be included. Thickeners are commonly incorporated to increase viscosity, reduce miscibility with water, e.g. as found in many boreholes, and certain other agents may be included to prevent premature reaction between the water and the aluminum. Density control agents in the form of bulk fillers or agents which decompose to form gas and thus aerate the the mass, may be introduced to control the density. Sensitivity is often affected by density.

in all these materials of the prior art, various attempts have been made to reduce their cost. While the use of inexpensive oxidizers such as calcium nitrate as an ingredient in explosives of this type has been suggested, this particular oxidizer has not generally been considered to be a desirable ingredient because compositions containing calcium nitrate tend to be quite insensitive. When calcium nitrate is combined with substantial quantities of water in a blasting slurry, for example, detonation characteristics would not have been expected to be satisfactory in the prior art. Nevertheless, since calcium nitrate is an inexpensive ingredient with abundant excess oxygen, it would appear to be a desirable ingredient in these explosives if it could be used.

It has also been suggested, as in US. Pat. No. 3,457,127, that explosive compositions of this general type might be prepared by using nitric acid per se as an important ingredient, reacting it with a suitable fuel in the course of preparation and in the presence of ammonium nitrate which serves to cool and thereby control the reaction. Because of its high endothermic heat of solution, ammonium nitrate is an attractive material for controlling reactions which might otherwise tend to run away. Nitric acid is highly corrosive material which is difficult to handle under field conditions. It is preferable for many purposes to be able to formulate a powerful explosive in the field, or without extensive mixing equipment, provided this can be done in a safe and efficient manner.

An object of the present invention is to obtain the benefits of using cheap calcium oxide as one ingredient, combining it with paraformaldehyde to produce an intermediate product that will serve as an efficient fuel in an explosive slurry. The reaction between calcium oxide and formaldehyde or paraformaldehyde is exothermic. However, it produces some water and in the presence of ammonium nitrate, which dissolves in water about as rapidly as the latter is produced, the reaction is kept under control. The temperature rise thus remains within safe limits. A further object is to generate a liquid in reacting calcium oxide and a formaldehyde which liquid contributes substantially toward formation of a continuous liquid phase slurry which can be detonated.

Other objects include production of a viscous explosive slurry in which various particulate ingredients will remain in stable suspension and which has resistance to water. Still other objects will appear more fully as a detailed description of preferred embodiment of this invention proceeds.

SUMMARY Calcium oxide is reacted in the presence of a formaldehyde, preferably paraformaldehyde and also in the presence of ammonium nitrate. Generation of water by the calcium oxideformaldehyde reaction dissolves the ammonium nitrate. This dissolving action, which is highly endothermic, is used to keep the primary reaction under control. Proportions of about 5 to 20%, by weight, of calcium oxide (burnt lime), 12 to 60% of ammonium nitrate, and about 7 to 35% of formaldehyde are reacted together to produce hexamethylene-tetramine, calcium nitrate and water. To these primary ingredients are added small amounts, i.e. 0.1 to 1% or more of guar gum or other gelling agents, and various amounts of other oxidizers, fuels and modifiers of conventional types used in blasting slurries.

DESCRIPTION OF PREFERRED EMBODIMENT Basically the present invention is based on the discovery that a reaction substantially as follows is an inexpensive and efficient way to produce the major components needed in a slurry-type explosive composition. The consistency of these slurry compositions, of course, may be varied within wide limits from thin slurries to semi-solid products. Other oxidizers such as ammonium nitrate, sodium nitrate, ammonium and/or alkali and alkaline earth metal chlorates and perchlorates and various fuels named below may be included. Basically the equation of the composition is as follows:

Approximately four molar parts of ammonium nitrate may be added to the reaction mixture to give appropriate energy and oxygen balance; however, the quantities so added may be varied from as little as 10% by weight of the total composition, to as much as 50% or more.

lt will be seen from the above that basically calcium oxide, ammonium nitrate, and formaldehyde, preferably a polymer such as paraformalde-hyde in appropriate proportions react to form hexamethylenetetramine, water and calcium nitrate. A little water may be added if desired. The proportions of water formed by the reaction are generally appropriate for slurrying the composition so that it is normally unnecessary to add other water; however, some water may be added where a thin slurry is needed. Conversely, the fluidity of the slurry can be reduced by adding larger proportions of other solids which take up water, such as ammonium nitrate or insolubles. Obviously, these compositions may be modified by adding oxidizers which are soluble or only partly soluble, such as other nitrates, chlorates, perchlorates, and the like, as is mentioned above. Particulate fuels, such as finely divided aluminum, coal, gilsonite, sugar and other carbonaceous materials can be added. Self-explosive particles of TNT, nitrocellulose, etc., can be included if desired.

The reaction set forth in the equation given above generates considerable heat which might quickly reach a temperature of 275 F or more in a batch of say pounds if no ammonium nitrate were included. By including appropriate proportions of ammonium nitrate, the temperature can be reduced as much as 100 F or more, thus making the mixing operation entirely safe. The type of granulation of the ammonium nitrate used is significant in controlling the rate of reaction, and especially the induction time. If all of the ingredients are in finely powdered form, the reaction in a mixing device starts quickly and may be completed within a minute or less. Under these conditions, of course, there may be higher temperatures encountered than in reactions with coarser materials, which start and proceed more slowly.

Compositions produced as above may contain considerable proportions of liquid. Ordinarily, it becomes desirable to thicken the slurry to a suitable consistency so that it will resist water penetration and prevent segregation of suspended solid particles. As thickener, various agents including guar gum may be used, but a particularly preferred one is a pregelled potato starch which has good compatibility with the type of slurry produced in the above reaction.

Slurries as produced according to this invention may be too dense and hence too insensitive for firing with reasonable sized inexpensive boosters. They may shoot satisfactorily in columns as large as four or five inches in diameter but not in smaller diameter charges. In order to increase their sensitivity, it will frequently be desirable to add a gasifying or aerating agent, or in some other manner to reduce the density. According to the present invention, this may be done by adding a small amount of a gas generating substance. Hydrogen peroxide may be used along with a catalyst such as manganese dioxide which will promote its decomposition. Nitrites, sulphites or carbonates may be used to generate oxygen or other gases for the same purpose. In a typical case about 0.1 to 0.3% of 35% H O may be added to the gas, proportions being by weight. Along with this, a small amount of magnesium oxide is added to catalyze the decomposition of the hydrogen peroxide.

Another advantage of the present invention is that not only does the composition form its own water by reaction but it also can heat itself under appropriate conditions to a reasonable and desirable working temperature, e.g., from ambient temperature up to as much as 200 F or more. This makes an explosive which is especially suitable for use in cold climates. It does not require special heating equipment. The composition may be prepared from the separate ingredients mixed on site without auxiliary heating equipment in coldest weather.

As noted above, particles of the various reactive components may be of various sizes. If a coarse ammonium nitrate is used, it may be slow to dissolve and therefore slow in controlling the reaction temperature. Finer particles may be needed if the calcium oxide is finely divided and reacts rapidly. In such a case it may be desirable to use at least a little finely ground ammonium nitrate to start the initial reaction and thus to give better control.

The simple ungelled slurry as produced above, without a thickener, is not water resistant, as may be desirable for use of the explosive in wet boreholes. The ungelled slurry sometimes can be used as such in dry boreholes, but in order to improve the water resistance for places where ground water is abundant, it is desirable to add a thickener, preferably a crosslinked thickener. Some mixture of both thickener and unthickener may be used. Guar gum may be used as thickener, or one of the starches, or a combination. Pregelled potato starch in proportions of 0.5 to about 3% by weight, based on the total composition, has been found highly desirable as already noted, because it gives a gel smooth structure which can become very firm if desired.

The quantity of formaldehyde or polymer thereof preferably is sufficient to give about stoichiometric propor tions with the calcium oxide. Smaller quantities may be used and the temperature better controlled but reactions of this type will give off ammonia, which is usually undesirable. The formaldehyde or paraformaldehyde tends to keep the solution neutral, that is with a pH of about 7.0. Any evolution of ammonia, of course, soon makes it strongly alkaline.

The invention will be further described in connection with specific examples.

EXAMPLE I In order to prepare a lOO-lb. batch of explosive, 4.068 kilograms of fine powdered calcium oxide were added to 31.85 kilograms of ammonium nitrate. Of the latter, 5 kilograms were finely ground and the remainder was in prill form. As noted above, part of the ammonium nitrate was ground to speed up the reaction, that is, to reduce the time required to form a slurry and to keep better control over the reaction temperature.

These ingredients were mixed in a cement mixer for about 3 minutes. The product reached a final temperature between 65 and 75 C. To the above was added a premixed batch of dry ingredients made up of 3 kilograms prilled ammonium nitrate, 0.095 kilograms of fine powdered manganese dioxide (Mn 0 and 0.90 kilograms of fine powdered potato starch. To obtain proper viscosity, the solution or slurry temperature was lowered by cooling to approximately 55 C before adding the dry pre-mix. Addition of the dry pre-mix to the slurry resulted in a further lowering of the temperature of the mixture by approximately 10 C. Immediately after adding the dry pre-mix material, hydrogen peroxide of 35% concentration was added in weight proportions of about 0.2% based on the total, to produce oxygen gas and thereby reduce the density. This peroxide was thoroughly mixed into the other ingredients. The mixture was then subjected to tests for density and blasting strength.

EXAMPLE ll Another slurry composition was made up of the following ingredients, percentage by weight: calcium oxide, 8.95%, ammonium nitrate, 76.67%, paraformaldehyde, 14.38%, totalling of these three ingredients. As these materials were mixed together, the mixture generated water and became liquid. To the resulting slurry 2% by weight of potato starch was added for thickening. The equation of the initial reaction appears to be:

In order to reduce density of the slurry, thereby reducing its critical diameter so that the material could be fired with a reasonable sized booster, 0.2% of manganese dioxide was added, along with 0.15% by weight of 35% hydrogen peroxide. This addition of gassing agent resulted in lowering the slurry density from approximately 1.4 grams per cc. to a density in the neighborhood of 1.2 grams per cc. At the latter density the critical diameter unconfined was less than 4 inches at 25 C. At still lower densities of 1.1 grams per cc. and at 25 C, detonation occurred in charge diameters of 3 inches. Following is a tabulation of the shot results:

Another 100-lb. batch of slurry was made up as follows: 8.32 kilograms of calcium oxide, finely powdered, was added to 23.77 kilograms of ammonium nitrate, making a total dry mix of 32.09 kilograms. These materials were first stirred together dry in a cement mixer. After such stirring, 29.4 lbs. (13.36 kg.) of paraformaldehyde was added. The ambient temperature was 50 F. The temperature rose at an almost linear rate, reaching 250 F. There was considerable turbulence and some of the material boiled over or overflowed at about 180 F, spilling part of the products on the ground. The material thus spilled was filled with gas, indicating that the chemical reaction was far from complete. Maximum temperature of 250 F was reached about seven minutes after mixing of all of the ingredients commenced. Thereafter the temperature began to drop. In about twelve minutes it had been reduced to about F. Thereafter it remained almost constant, with only very gradual cooling for a period of some minutes.

- At a time 23 minutes after adding the formaldehyde, the

EXAMPLE IV Another composition was made up by first mixing calcium oxide and ammonium nitrate in a mixer, prior to adding prilled paraformaldehyde. The starting temperature was 55 F. Maximum temperature was reached in about 15 minutes, 160 F in this case, showing a total temperature rise of 105 or 58 C. Proportions were 8.95 lbs. calcium oxide (4.068 kg), 76.65 lbs. ammonium nitrate (34.854 kg), 14.38 lbs. paraformaldehyde (6.536 kg). The dry ingredients were mixed for about 1 minute before the formaldehyde was added.

After the reaction was complete the temperature was 65 C. Some ammonia was still being evolved thirty minutes after the maximum temperature had been achieved, as noticed by the odor. This material became very fluid and could easily be pumped. As a matter of fact, it could have been pumped with a lower liquid content. The density of the unthickened mix was 1.40 grams per cc. at 55 C. There was some slight segregation of ingredients in this mixture at 56 C. The resulting slurry was thickened by adding 2% of pre-gelled potato starch and was tested again for density, which proved to be 1.39 g/cc.

The thickened slurry described just above was tested by firing it in 6-inch and 4-inch diameter cardboard tubes. The temperature of the 6-inch tube at time of firing was 54 C and that of the 4-inch charge was 46 C. Both charges fired very well with a standard booster. A sample of the non-thickened material having some segregation was fired successfully in a 6- inch diameter tube at 57 C. In the latter shot the charge was placed on a steel plate ii-inch thick. The firing produced a bulge about 4 inches in depth in the plate but did not penetrate it.

All three shots were considered to be successful detonatrons.

EXAMPLE V A composition was made up of 4.068 kg. of calcium oxide, 34.85 kg. of ammonium nitrate prills, and 6.54 kg. of paraformaldehyde powder. For comparative purposes this was repeated using finely powdered ammonium nitrate instead of the prilled ammonium nitrate. The initial temperature in the latter batch was 27 C. In five minutes it had dropped to 26.3 C and six minutes later to 26. 1 C. Thereafter the temperature began to rise. 2 minutes later it had gone up to 28.4 C, another minute later it was 33 C, two minutes later 51 C. Then the temperature began to drop. After 2 minutes it was 45 C; 2 minutes after that it had dropped to 41 C. The slurry first became fluid at around 51 C and remained so thereafter. The slurry was cooled further by refrigeration to 37.5 C in 2 minutes, 32 C in 5 additional minutes, and to 31 C in 4 additional minutes after that.

It is noted that by replacing the prilled ammonium nitrate with ground ammonium nitrate, the induction time for the reaction was reduced almost to zero. The prilled material took some time before it started to react. Except for greatly reduced reaction time, however, and sharper temperature rise with ground ammonium nitrate, the reactions otherwise were very similar.

EXAMPLE VI Another 100-lb. batch was made up of 18.3 lbs. of calcium oxide, 52.3 lbs. ammonium nitrate, and 29.4 lbs. of paraformaldehyde, with generally similar results.

EXAMPLE VII Another 100-lb. batch was prepared, using 8.95 lbs. of calcium oxide, 76.68 lbs. of ammonium nitrate, and 14.38 lbs. of paraformaldehyde. To this composition was added 2% of potato starch as a thickener, as described above. All the ingredients were added simultaneously to the mixer and, the mixer was then started up. The mixture had an initial temperature of 50 F which rose to 168 F but some hot spots at considerably higher temperature were noted. Discounting these, the overall temperature rise was about 118 or 66 C. Maximum temperature was reached in less than 2 minutes. Only a small part of the ammonium nitrate had reacted because the finely ground material in this instance stuck to the bottom of the mixer. This caked material was scraped into the fluid portion, using a paddle board. Such mixing caused the batch to drop slightly in temperature to 152 F. The temperature rise apparently would have been less if the mixture had all been stirred adequately in the first place.

EXAMPLE Vlll Another batch was prepared in the same manner, except that the amount of potato starch added was 1%. This quantity appeared to be adequate to prevent the solids from segregating. Using ground ammonium nitrate, segregation tendencies are reduced at temperatures below F, and the resulting slurry is reasonably stable without a thickener.

In the example just given, the potato starch was added before the reaction was complete but after the material had been reacting for about three minutes. The batch was still granular in texture, before the starch was added. The temperature began to climb immediately after the mixer started, but at a much slower rate than with the finely ground ammonium nitrate. This reaction was complete after about 10 minutes, following starting of the cement mixer. The temperature rise in this case was 133 F, reaching a maximum of F at 8.5 minutes after the mixer started. In this case there were some remains of the previous mixture around the corners of the mixer which may have affected the induction time. The temperature began to drop ofi immediately after maximum was reached and came down to about 170 F in 3 minutes. Thereafter it dropped on down to 160 F.

EXAMPLE IX A 5041). batch was made up based on the formula Ca0 2AN 311C110. Theoretically this should have produced one mole of calcium nitrate, one-half mole of hexamethylenetetramine, and 4 moles of water. In this case the prilled ammonium nitrate was mixed along with the granular or powdered calcium oxide and paraformaldehyde. The induction time was between 20 and 21 minutes. From an initial temperature of 50 F, the maximum temperature of 260 F (126 C) was reached in 23 minutes. Thereafter the temperature dropped from 260 to F after 3 minutes.

Some caked material from the previous mix, No. VIII still remained in comers of the mixer. This may have had a minor effect but was not regarded as significant.

The product just described was taken out of the mixer immediately after the reaction was completed. It could not be detonated by a No. 6 electric blasting cap at 75 C in a 4-inch diameter charge confined in a cardboard tube. Its density was not measured but it was probably about 1 .45 grams per cc.

It was noted that the time required for mixing in Example IX was about 3 minutes longer than when the calcium oxide and ammonium nitrate were first mixed together and the paraformaldehyde added later. However, in this case the initial temperature was about 5 cooler than with the earlier mixes and only about half as much material was used. This may have affected the reaction time.

The composition of Example [X was tested in a 4-inch charge, 6.07 kilograms being placed in a cardboard tube, filling it to a height of 47.8 centimeters. This material had a density of about 1.57 grams per cc. It failed to fire in this 4- inch diameter at 18 C. Other samples were tested in S-inch tubes, using compositions of Examples VII and VIII for comparison. These had densities respectively of 1.44 grams per cc. and 1.42 grams per cc. At a temperature of 26 C they all failed to fire. The density apparently was too great for these particular compositions in columns of the diameters indicated.

Compositions of Example 1X were tested also in tubes of diameters of 5, 4 and 3 inches respectively. These had densities respectively of 1.6, 1.65, and 1.67 grams per cc. All of them failed at temperatures of 26 or 27 C. Composition VIII was tested in S-inch and 4-inch diameters at densities of 1.44 and 1.49 respectively. The first was tested at 25 C and the second at 18 C. Both of these failed with a standard booster. Here again, apparently the densities were too great for these charge diameters. It is believed that they would have fired successfully in 6-inch or larger column sizes.

The composition of Example Vl also was tested in charge diameters of 6, 5, and 4 inches respectively. These had densities respectively of 1.42, 1.32, and 1.37 grams per cc. All of these were tested at 25 C. The 6-inch charge fired very well with a detonation velocity of 4,230 m/sec which is considered an excellent shot. The -inch tube fired but its velocity was substantially less, about 2,535 m/sec. This was considered fair. The 4-inch charge failed.

Mix No. V11 above, which included hydrogen peroxide as a gassing agent, was placed in tubes of 5-inch, 4-inch, and 3- inch diameters respectively with respective densities of 1.21 1.11, and 1.10 g/cc. All ofthese shots were tested at 25 C. All three detonated. The 5-inch column showed a detonation velocity of 3,520 m/sec. Velocities of the other two were not measured but they appeared to be hard detonations, that is, they were apparently of high velocity.

EXAMPLE X Another composition was made up of 4.068 grams of calcium oxide, 17.427 kg of ammonium nitrate, and 6.536 kg of paraformaldehyde. These materials were stirred together and a reaction occurred which caused the temperature to reach a maximum of 1 17 C and the solids went substantially into solution in the water which was generated. To this mixture there were added, as dry ingredients, 17.427 kg of ammonium nitrate prills, 0.45 kg of potato starch and 0.095 kg of manganese dioxide. The latter dry ingredients were added at a temperature of 67 C in the solution. These materials were stirred in and immediately thereafter 0.190 kg of 35% hydrogen peroxide was added. The final mixing temperature after complete mixing was 43 C.

EXAMPLE XI On the basis of the experience gained in the above examples, a preferred procedure was followed, as will now be described. 4.068 kg of calcium oxide were combined with 34.854 kg of ammonium nitrate, of which about 3 kg was finely ground and the remainder was prilled. To this was added 6.536 kg of powdered paraformaldehyde. These dry ingredients were mixed together. The mixture temperature rose to 73 C and was then cooled to about 64 C, with a resulting slurry or suspension of solids in a continuous liquid (water) phase. Thereafter, a mixture of a second group of dry ingredients was stirred in consisting of 4.0 kg of ammonium nitrate, 0.908 kg of potato starch, 0.095 kg of manganese dioxide. After the latter dry mixture was stirred in, there was added 0.19 kg of 35% hydrogen peroxide immediately after the dry ingredients were stirred in. The mix temperature after adding all these ingredients was 57 C.

The composition thus produced was tested in 3 and 4-inch charge diameter tubes. The 4-inch charge had a density of 1.25 g/cc and was fired at 25 C. It detonated very well with detonation velocity of 2,690 m/sec. The 3-inch charge with density of 1.11 at 25 C detonated also, but its velocity apparently was less. This was true also of another 4-inch charge having a density of 1.14 g/cc. Apparently it may not be useful to go below a density of about 1.2, as excessive aeration reduces power. At least this was the indication in this particular test.

EXAMPLE X11.

The test in Example X] was substantially repeated, using the same quantities of calcium oxide and paraformaldehyde, but using a total only of 34.854 kfof ammonium nitrate of which 3 kg were withheld for adding later along with the potato starch and manganese dioxide. Of the ammonium nitrate used to make this composition, about 5 kg was finely ground. When the calcium oxide, AN, and paraformaldehyde were stirred together, a solution was formed in about 3 minutes. The mix reached a temperature of between 65 and C. Thereafter it was cooled to 55 C after which 3 kg of the prilled ammonium nitrate taken out of the pre-mix was added, along with the potato starch and manganese peroxide. Thereafter the hydrogen peroxide was added in quantity of 0.95 kg.

EXAMPLE Xlll Examples X1 and X11 were repeated, except that the quantity of peroxide used was 0.15%. The initial solution temperature was around C maximum. Thereafter the solution was cooled to 55 C and 3 kg of dry prilled ammonium nitrate was added along with the potato starch and the manganese oxide. After addition of these dry ingredients the temperature was 50 C. This material appeared to be drier than mix of Example X11. It was more difficult to mix the hydrogen peroxide into the slurry. The only significant change in procedure was that the initial temperature of the cement mixer was somewhat higher on mix No. X111 than on No. XII because the mixer had just been washed with steam and hot water.

The products of Example Xlll were tested in charge diameters of 4, 3, 2.5, and 2-inch diameters. The 4-inch charge at a density of 1.25 g/cc detonated with a velocity of 2,640 m/sec. The 3-inch charge with density of 1.13 g/cc also detonated but velocity was not measured. The 2.5-inch charge, whose density was not determined, detonated also. The Z-inch charge failed at 25 C.

From the foregoing, the following conclusions may be drawn. Effective blasting agents may be made by mixing together calcium oxide or burnt lime with ammonium nitrate and paraformaldehyde to form a slurry, generating the necessary liquid for producing a continuous liquid phase in the process. To this slurry are added a small amount of thickener and a small amount of gassing agent. Additional oxidizer may be added or not as desired. In lieu of ammonium nitrate added in the second stage, other oxidizers, such as sodium nitrate and/or one or more of the ammonium alkali metal chlorates and perchlorates may be added in moderate quantities. Other gassing agents than hydrogen peroxide, such as nitrous acid, nitrites, etc., may be substituted or used with H 0 By appropriate aeration or other suitable procedures to keep density within limits of about 1.15 to 1.40, effective blasting agents are produced. Those which are at the denser end of this scale are more difficult to detonate but they can be detonated in large diameters, as a rule. When detonated they are extremely powerful. Those toward the lower end of the density scale are more easily detonated but they lose some of their power if there is excessive aeration. These explosives are useful in hard rock blasting, construction work, oil well fracturing, seismic prospecting and in many other ways.

By using ammonium nitrate, or most of it, in the original mix, the temperature is well controlled and conversion of the formaldehyde to hexamethylenetetramine appears to be substantially complete. If the products are in chemical balance there is no substantial evolution of ammonia although a small amount of ammonia may be generated in some cases. It is desirable to keep the pH of the solution reasonably near neutral and for this reason as well as for comfort of the personnel working with it excessive ammonia generation should be avoided.

To the slurries described above there may be added other fuel materials such as aluminum, carbonaceous fuels such as finely ground coal or gilsonite, self-explosive particles such as TNT, smokeless powder granules, and the like as is well known in the art. These are not necessary, however, for sensitization except in unusual cases. When slurries are intended for low temperature use it may be desirable to add a small amount of fine aluminum or some of the self-explosive particles for the purpose of increasing sensitivity. Ordinarily this is not necessary and usually it is not desirable because of the cost of the added ingredients.

The compositions thus produced are relatively very inexpensive. They can be produced safely in a plant or in the field with relatively simple equipment. The components are safe to handle and are almost universally available. The methods employed for combining them are safe, extremely simple and easily regulated. They are preferably in slurry form, i.e. having undissolved particles suspended in a continuous liquid phase, and desirably are thickened to a gel consistency. The latter is not always necessary, so long as the whole composition is viscous enough to remain reasonably homogeneous and free from substantial separation or segregation of solids.

It will be obvious to those skilled in the art that various modifications may be made without departing from the spirit and purpose of the present invention. It is intended by the claims which follow to cover such as broadly as the state of the prior art may properly permit.

What is claimed is:

1. An explosive composition in slurry or gel form comprising substantial proportions of ammonium nitrate as a first oxidizer, and substantial proportions of the reaction products of calcium oxide and a formaldehyde reacted in the presence of said ammonium nitrate, said reaction products including a fuel and including calcium nitrate as a second oxidizer, said composition containing enough liquid to form a substantially continuous liquid phase.

2. Composition according to claim 1 wherein the formaldehyde is paraformaldehyde.

3. Composition according to claim 1 which contains a thickener or gelling agent.

4. Composition according to claim 3 wherein the thickener or gelling agent is potato starch.

5. Composition according to claim 1 which includes an aeration agent to reduce its density significantly.

6. Composition according to claim 5 wherein the aeration agent is hydrogen peroxide.

7. Composition according to claim 1 which contains a density reducing agent and which has a final density between 1.15 and 1.4 g/cc.

8. The process of preparing an explosive composition which comprises the steps of exothermically reacting solid particulate calcium oxide with a formaldehyde in the present of solid particulate ammonium nitrate to control temperature rise of said reaction, thereby generating (l) a liquid which dissolves endothermically some of said ammonium nitrate, (2) a fuel and (3) calcium nitrate, and forming a slurry having a substantially continuous liquid phase which includes said generated liquid and having undissolved particulate solids dissolved therein.

9. Process according to claim 8 wherein an aerating agent is added.

10. Process according to claim 8 wherein a thickener or gelforming agent is added.

11. Process according to claim 8 wherein a combination of dry ingredients, including a gelling agent, is added to the slurry.

12. Process according to claim 11 wherein an aerating agent is included in the composition. 

2. Composition according to claim 1 wherein the formaldehyde is paraformaldehyde.
 3. Composition according to claim 1 which contains a thickener or gelling agent.
 4. Composition according to claim 3 wherein the thickener or gelling agent is potato starch.
 5. Composition according to claim 1 which includes an aeration agent to reduce its density significantly.
 6. Composition according to claim 5 wherein the aeration agent is hydrogen peroxide.
 7. Composition according to claim 1 which contains a density reducing agent and which has a final density between 1.15 and 1.4 g/cc.
 8. The process of preparing an explosive composition which comprises the steps of exothermically reacting solid particulate calcium oxide with a formaldehyde in the present of solid particulate ammonium nitrate to control temperature rise of said reaction, thereby generating (1) a liquid which dissolves endothermically some of said ammonium nitrate, (2) a fuel and (3) calcium nitrate, and forming a slurry having a substantially continuous liquid phase which includes said generated liquid and having undissolved particulate solids dissolved therein.
 9. Process according to claim 8 wherein an aerating agent is added.
 10. Process according to claim 8 wherein a thickener or gel-forming agent is added.
 11. Process according to claim 8 wherein a combination of dry ingredients, including a gelling agent, is added to the slurry.
 12. Process according to claim 11 wherein an aerating agent is included in the composition. 